1. Field of the Invention
The present invention relates to an image sensor and method of fabricating the same, and more particularly, to an image sensor provided with a bonding pad that can be prevented from being eroded by a developer, and a micro lens with an improved concentration efficiency, and a method of fabricating the same.
2. Description of the Related Art
In general, image sensors are a semiconductor device, which converts an optical image into an electrical signal, and are classified into charge coupled device (CCD) type image sensors and complementary metal oxide semiconductor (CMOS) type image sensors. The CMOS type image sensor is generally abbreviated as ‘CIS’.
The CCD type image sensors and the CMOS type image sensors commonly have a light receiver that receives light and converts the received light into an electrical signal. The CCD type image sensors transmits the electrical signal through a CCD and converts the electrical signal into a voltage at their last terminal, whilst the CMOS type image sensors convert the electrical signal into a voltage at each pixel and output the converted voltage to an outside.
In the meanwhile, light passes through a multi-layer consisting of a micro lens, a color filter and a light shielding layer before it is incident into the image sensor and reaches the light receiver. This multi-layer is an element to improve the picture quality or reproduce colors, and needs to be optimized so as to realize good picture quality.
Hereinafter, a related art image sensor will be described with reference to FIG. 1.
FIG. 1 is a schematic sectional view of an image sensor 100 according to the related art, and omits a photodiode and the like.
The related art image sensor 100 is configured to include a substrate 1, an element layer 2 formed on the substrate 1, a bonding pad 4 formed on a bonding pad area 12 of the element layer 2, a passivation layer 3 covering the bonding pad 4 and formed on the element layer 2, color filter patterns 6, 7, 8 sequentially formed on a pixel array area 11 of the passivation layer 3, an overcoating layer (OCR) 9 formed on the color patterns 6, 7, 8, and a micro lens 21 formed on the OCR 9.
According to the related art, the passivation layer 3 is etched to open the bonding pad 4, and then consecutive photomask process steps are performed to form the color filter patterns 6, 7, 9, the OCR 9, and the micro lens 21. The bonding pad 4 is generally made of aluminum (Al).
Then, the alkaline developer used for developing photoresist films in the consecutive photomask process steps hardens the bonding pad made of pure Al, and may sometimes cause a contaminant 30 to be created on the bonding pad 4.
Also, the hardening and the contamination of the bonding pad 4 cause function fail or the like due to pin contact failure during the probing test. At this time, deep probing is only a method.
In addition, as shown in FIG. 1, in the prior art image sensor 100, a clearance 22 between the micro lenses 21 is generated to deteriorate the concentration efficiency since light that is incident into the clearance 22 is not induced into the photodiode.